Two-way telephone transmission



- 'Aug'.. 23, 1927.

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UlillTED STATES PATENT OFFICE.`

HAROLD S. HAMILTON', 0F NEW YORK, N. Y., ASSIGNOR T0 AMERICAN TELEPHONE AND TELEGRAPH COIiIPNY, A CORPORATON OF NEW YORK.

TWCNVAY TELEPHONE .LBulhl'SIYIISSION.`

Application filed November 24, 1926. Serial No. 150,496.

This invention relates to two-way telephone systems, and more particulary to twoava y ltelephone systems including a tourwire circuit having paths adapted for transmission 1n opposite directions and a` conn bined wire and radio circuit having outgoing and `incoming' wire paths connectedrto the Viourwvire circuit. y

'lhe object of the invention is the minf iinization oi the false operation oi echo suppressors in the circuits by noise or static entering the Wire sections or the system from the radio link.

rthis object is attained by providing `for the disabling oit the incoming wire path oi the combined wire'and radio circuit in re spouse to currents of a given value or a greater value 1n the corresponding outgoing wire path, and regulating the currents tlowing over the outgoing path so that they will always have a value suilicient to effect the disabling oi the incoming path.

My invention will be more clearly understood when the following description and discussion are read with reference to the accompanying drawing, which shows indiagramniatic i'orm a telephone system to which the` invention is applic-able.

it the lei't or the drawing there isshown an ordinary tour-wire circuit equipped with one-way repeaters or ainpliiiers. i 'this tourwire circuit is connected at A to the two-wire 'line L1 with the usual hybrid coil and 'balanc-v ing network. lhis four-wire circuit, urther1nore,`is equipped w ith the ordinary echo suppressor apparatus. The iV--i ampilierdetector, operated by outgoing currents, controls the incoming transmission path through the operation or the relay R1. lriniilarly, the Alik-W amplifier-detector, operated by currents in the incoming path, controls the transmission over the upper path by the operation of the relay R2.

ljetween the `rourwvire circuit and the distant two-wire line L2 there is shown aconn bined Wire and radio circuit. The two-wire sections ot this circuit are joined by the radio link, as shown. 'l` he lett-hand wire section oi the combined circuit, which will be given closer consideration, is connected at C to B of the four-Wire circuit by a cord circuit rept-Eater connection or by other suitable connection, the usual hybrid coils and balancing networks being included. rlhe outgoing coimection to the radio link is through the at all times, Vsince the volume ot transmisH sion which may be applied to the twoterininals ot the lourwvire circuitlvaries over a considerable range. Hence at times-:tor instance, it a weak talker is talking through riiovery the outgoing transmission path-the W-Q aniplilier-detector Will fail to operate. This condition is practically satisfactory provided that the noise interference is no greater than that ordinarily received troni wire lines.` y v it, however, the four-Wire circuitis connected 4to a'combined: circuit including a :radio link, the interference from noises `or static may be great, suliicient to upset the proper operation of the echo suppressor devices. More specifically, the Ill-Vif ampliliersdetector may be operated by the interi'er ing currents at a tiniewhen a weak talker through A. has not control oi' the circuit due to `the tact 'that the voice currents are too weak to operate the 1yV-E amplitier-detec tor. ln such a case it is obvious that the outgoing transmission from A is seriously interfered with.

The section ol the combined wire and radio circuit between C and D and E is shown equipped with echo suppressor and singing suppressor apparatus. T he V-E amplilier detector of this section ot the circuit is operated byk outgoing` currents in the upper wire path. The outgoing transmission path is normally blocked in 'trout of the radio transmitter at D, being short circuited. will'heu the Vil-E amplilier-detector operates. it clears the outgoing transn'iission path, the operation of the relay R, removing the short circuit; it also disables the incoming transmission path through the operation of the relay It, which places a short circuit on the incoming path. rlfhe E-W amplilier-detector ot' this section or' the circuit operates on currents in the incoming path to place a short circuit on the outgoing path'througli the operation ot the relay It is obvious, upon an examination ot the circuit, that clipping will result unless the l/V-Jt amplifierdetector of the combined circuit functions Without fail; that is, there must be full operation on the outgoingttransmission path. It is also obvious that an irregular operation of the corresponding E- l'V amplifier-detector, such as might be caused by noise or static coming in at E, will prevent the clearing of the outgoing trans-- iiiissioii path unless control of that path is a iured by the certain functioning of the H E amp]iliei '-detector.V To take a specific case, a weak talker through A n'iust be aine to control the transmission path through 1) in spite of the interfering noise or static re cived atl E.

rlhe problem outlinedy above is solved by adjusting the lV-E amplifier-detector ot' the combined circuit soy that it Will operate at a given value of the outgoing currents in the Wire section or at a greater value, and the value of t-liese outgoing currents is regulated so that it Will always be sul'licient to cause the full operation of the amplifierdetector. Af suitable means for attaining the desired result Vis a vregulating network N which should be placed in the outgoing path before the one-Way repeater or amplilier P.

By the method described above, even a Weak talker through A is enabled to control the youtgoing transmission path. His voice may notbe strong enough to operate the echo suppressor on the four-Wire circuit, but the voice currents in the outgoing Wire path of the combined Wire and radio circuit will be regulated so that full operation of the W-Iil ainplifiendetector of' the combined circuit will be obtained. Thus the outgoingl path is cleared, and static or noise entering at E is prevented from hindering the clearing ot' the outgoing path or blocking that path through the operation of the relay R5. Also,

ot' course, currents due to noise or static entering the path EC, are prevented from being passed on to the incoming path BA of the four-Wire circuit andl1 falsely operating the If--V ai'nplitier-detector o'l' that circuit.

`vWhat is claimed is:

l. In a two-Way telephone system includ* ing a four-Wire circuit having two paths adapted Vfor transmission in opposite directions and a combined Wire and radio circuit having` outgoing and incoming Wire paths connected to said four-wire circuit, the method ol preventing the application ot static and noise to the four-wire circuit. which consists in disabling said incoming path of the combined'- wire and radio circuit in response to currents of a predetermined. value in said outgoing path, and regulating the currents entering said outgoing path so that they Willliave the predeterminedvaine whatever may be the strength ot the voice currents applied to said pathflroin the tour-- wire circuit.

2. In a two-Way telephone system including a four-Wire circuit having two paths adapted tor transmission in opposite dii-er tions, a combined Wire and radio 'circuit liar ing outgoing and incoming Wire paths con* nected to said four-Wire circuit, and voice yoperated means in said outgoing path Vtoidisabling the opposite incoming path, rncv method ot preventing the application ot static and noise to the four-wire circuit which consists in disabling said incoming path of the combined Wire and radio circuit` when the currents in said outgoing path reach a predetern'iined value, and regulating the currents entering said outgoing path so that they will'have the predetermined 'vaine Whatever may be the strengtliolf the voice currents applied tosaidpath troni the iourwire circuit.

In testimony whereof, I have signed my name to this specilicationv this 23rd day ci `Noveinhei" 1926. 

